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Particulate matter (PM) can have adverse effects on human health. Moreover, because the mechanisms of PM formation and behavior in the atmosphere are notably complicated, to reduce PM concentrations effectively and meet environmental standards, source-receptor relationships must be clearly understood. Stable isotope ratios can be used to detect chemical processes and distinguish sources. In environmental science, especially in research on aerosols, stable isotope ratios have proven to constitute a powerful tool for source identification. However, there are few long-term studies of isotope fractionation during secondary aerosol formation. In this study, stable nitrogen isotope ratios (d 15 N) of ammonia gas (NH 3), nitrogen dioxide gas (NO 2), nitric acid vapor (HNO 3), particulate nitrate (NO 3 À), and ammonium (NH 4 þ) in suspended PM (SPM) were analyzed to investigate seasonal trends and isotope fractionation during aerosol formation for long term sampling in Akita, Japan. The results indicated that d 15 N-NH 4 þ in SPM and d 15 N-NH 3 gas ranged from 1.3& to 38.5& (mean 16.1&) and from À33.6& to À0.0& (À16.9&), respectively. Furthermore, d 15 N-NO 3 À (SPM) and d 15 N-NO 2 and d 15 N-HNO 3 (gaseous) ranged from À4.6& to 4.8& (mean À0.5&), from À8.2& to À3.1& (À5.4&), and from À7.5& to 2.7& (À5.0&), respectively. The mean annual isotope fractionation factors for transformations from gaseous NH 3 to NH 4 þ in SPM, from gaseous NO 2 to gaseous HNO 3 , and from HNO 3 gas to NO 3 in SPM in the atmospheric environment were þ33.3&, þ0.5&, and þ4.9&, respectively. Isotope fractionation of NH 4 þ in SPM was much higher than that of NO 3 in SPM. As the chemical reaction from gaseous precursors progressed, d 15 N-NO 3 in SPM became steadily heavier.

Knowledge of black carbon (BC) concentrations and size distributions within surface snow inAntarctica is limited. However, these measurements are important to understanding global aerosol transport from combustion sources, and BC contributes to positive radiative forcing. This study analyzed the concentrations and size distributions of BC and inorganic ions in snow samples collected at the Syowa station in Antarctica from April to December 2011 and along a traverse route to an inland (Mizuho) station. The BC size distributions in snow were bimodal with mass median diameters of~140 and~690 nm. We also estimated the mass median diameter from unimodal distributions and found smaller diameters than were reported by other studies. The mass concentrations of BC in snow were higher in inland samples than in Syowa samples. Among Syowa samples, the BC concentrations in December (2117.3 ng L −1 on average) were higher than in other periods (288.2 ng L −1 on average). The December samples experienced ambient temperatures above 0°C, and the atmospheric BC concentrations did not increase simultaneously. Inorganic ions originated from the ocean and decreased with increasing distance from the coastal area. We conclude that the BC concentrations in surface snow increased mainly by postdeposition processes through the loss of water mass due to melting, evaporation, and sublimation. Our study is the first to report detailed BC concentrations and size distributions in eastern Antarctica, and the results will help to evaluate BC global transport, the snow albedo estimations in this region, and the climate impacts of BC.

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